Add predicates hasInput and hasOutput

[rjyounes]

We already have isProducedBy, but these are useful for workflows and their definitions. Useful for Determination.

[rjyounes]

How about developing a sub-gist for process and workflows?

Ryan, Doug: yes.
Ryan: belongs in gist, not a sub-gist.
Rebecca: may get complicated, with dependencies, loops, etc. We could work on it and see whether it evolves into something large enough for a new sub-gist or small enough for gistCore.

Working: Rebecca (chair), Doug, Ryan, Jamie, Cheryl
Reviewers: Michael, Dan, Pel